Pepsins work only in the stomach to start the breakdown of proteins in food. Enzymes in the small intestine finish the digestion of proteins into amino acids so they can be absorbed.
The primary hormone produced by stomach cells is gastrin, which controls acid secretion and stomach contractions. Gastrin stimulates the release of hydrochloric acid that, in turn, interacts with pepsinogen to activate pepsin and start the protein digesting process.
While most of the digestive system has two thick layers of smooth muscle within its walls, the stomach has an extra layer of muscle that enables complex grinding movements. Low frequency, sustained muscle contractions in the upper stomach create pressure inside the stomach that helps stomach emptying. In the lower stomach, wave-like contractions aka peristalsis occur.
The muscle contractions become stronger as they move toward the sphincter between the stomach and small intestine. As the contractions reach the end of the stomach, muscles contract, pushing food back and up into the stomach. As food becomes chyme in the stomach, it is slowly released into the small intestine for further digestion and absorption of nutrients.
Some pet owners mistakenly assume nutrients are absorbed from the stomach. In reality, the stomach absorbs very few substances. Small amounts of water may be absorbed across the stomach wall, as are small amounts of some fat-soluble medications, such as aspirin and nonsteroidal anti-inflammatory drugs, and alcohol.
The information in this blog has been developed with our veterinarian and is designed to help educate pet parents. The esophagus is a small hose-like tube, which connects the mouth to the stomach.
As it leaves the mouth, the esophagus follows a straight path through the neck and chest, passing near the heart through the diaphragm muscle and finally entering the stomach. The walls of the esophagus are composed of muscles, which move in wave-like contractions to push food into the stomach. When there is no food in the esophagus, the walls of the esophagus collapse in on each other, making a closed space. Surgery on the esophagus is always difficult because of its location within the chest and its slow rate of healing.
The sole function of the esophagus is to carry food from the mouth to the stomach. The dog's stomach is a sac-like structure designed to store large volumes of food and continue the digestive process. The esophagus carries food to the stomach, where it enters via a valve-like structure called the cardiac sphincter.
On the interior surface of the stomach is a series of folds called gastric folds. These folds function to help grind and break down food. The stomach lining secretes gastric acid and enzymes to further digest food.
Once this part of the digestive process is complete, the partially digested food exits the stomach through the pyloric sphincter and enters the duodenum the first segment of the small intestine. Once eaten, most food leaves the stomach within twelve hours after entering.
The small intestine is a tube-like structure which extends between the stomach and large intestine. It is the longest portion of the intestinal tract and is about two and a half times the animal's total body length. An animal twenty-four inches long would have about sixty inches of small intestine. The small intestine in the dog has three parts. The first portion, which attaches to the stomach, is the duodenum.
In a forty-pound dog, the duodenum is roughly ten inches long. The middle and longest portion is called the jejunum. The shortest part is the ileum, which connects to the large intestine. The duodenum attaches to the stomach and is relatively short.
It does, however, have very important functions. The gallbladder and pancreas connect to the duodenum by the bile and pancreatic ducts, respectively. Enzymes and other secretions that are important for digestion are produced by the liver and pancreas and pass through these ducts to mix with the food in the duodenum.
It may eliminate the need for barium studies because gastric motility; wall thickness and architecture; and, to a lesser extent, luminal contents may be evaluated sonographically. In addition, ultrasound examination is quicker than an upper gastrointestinal series and may be equally sensitive and specific for detection of gastric disease.
Ideally, sonography should be performed after a hour fast and before barium is administered. If needed, intraluminal gas can be removed by an orogastric tube and the stomach distended with fluid to act as an acoustic window. For evaluating stomach wall layers, 7.
Ultrasound has been used to help diagnose gastric neoplasms, 39 — 46 inflammation or infection, 47 ulcers, 48 foreign bodies, 45 , 49 pyloric hypertrophy, 50 gastric mineralization, 51 and gastroduodenal and gastrogastric intussusceptions, 52 , 53 and to evaluate gastropexy sites.
The appearance of the stomach varies with the amount of distention and the extent of luminal contents. When empty, the stomach may have a wagon-wheel appearance because of infolding of rugal folds Fig. This is especially noticeable in the cat, and the empty stomach is sometimes mistaken for an abnormal kidney by inexperienced sonographers. With increasing distention, rugal folds become less conspicuous. Stomach wall thickness in dogs is 3 to 5 mm depending on the location and size of the dog, with larger dogs having a thicker stomach wall.
The mean number of peristaltic contractions observed ultrasonographically in dogs has been reported to be 4 to 5 contractions per minute. The position of the stomach is a useful indicator for localization of some extragastric abnormalities in the cranial abdomen. Some diseases of the liver, spleen, pancreas, and diaphragm may affect the stomach. The relation between the stomach and a particular extragastric abnormality may help define the primary organ involved or the nature of the primary lesion.
Because the stomach is in close apposition with the liver, changes in size or position of the liver may cause a change in position of the stomach. Generalized hepatomegaly often produces caudal and dorsal displacement of the stomach. Thus on the lateral view, generalized hepatomegaly often produces caudal and dorsal displacement of the pylorus and body of the stomach.
This displacement changes the axis of the stomach so that the axis is no longer parallel with the ribs Fig. On the ventrodorsal or dorsoventral view, generalized hepatomegaly often causes displacement of the body and pylorus of the stomach caudally and toward the left Fig.
The Stomach. Anatomy In the normal dog and cat, the empty stomach usually lies cranial to the last pair of ribs, 1, 2 but it may extend slightly caudal to the costal arch. Radiographic Examination Preparation Ingesta within the stomach may obscure some lesions or simulate other lesions and thus create false-negative or false-positive results.
Normal Radiographic Findings The stomach is easy to recognize by its location and shape and the content of gas, ingesta, or both. A, Lateral view of a cat. The gastric axis is parallel with the ribs. B, Ventrodorsal view of a dog. The gastric axis of this dog is approximately perpendicular to the spine.
C, Ventrodorsal view of a cat. The stomach is acutely angled with the pylorus located closer to midline than in the dog; this is a consistent species difference. The fundus is located dorsally and on the left, whereas the pylorus is located ventrally and on the right. B, Computed tomographic image of a normal dog in dorsal recumbency at the level of the stomach.
Fluid fills most of the fundus F and part of the pylorus P , and the gas bubble floats near the midline. A, Ventrodorsal view, in dorsal recumbency.
Gas is located in the body and pyloric antrum. Fluid settles dependently to fill the fundus and body. In this dog, there is a small amount of barium trapped in the pyloric antrum. B, Dorsoventral view, in ventral recumbency. Gas rises to the fundus and fluid settles dependently to fill pyloric portions and part of the body. C, Left lateral view. Gas rises to the pyloric portion, and fluid settles dependently to fill the fundus and body.
D, Right lateral view. Gas rises to the fundus and body, when there is some barium adherent to the mucosa. Fluid settles dependently to fill the pyloric portion.
A, Left lateral view. Gas rises to the pyloric portion black arrows. In this dog, there is also some gas trapped in the fundus. Fluid settles dependently to the body, which is difficult to see. B, Right lateral view. Gas rises to fill the fundus and body black arrows. Fluid settles dependently to the pyloric portion, which appears as a soft tissue mass white arrows. Note the multiple curvilinear filling defects in the fundic region of the stomach. These filling defects are the rugae.
B, Dorsoventral gastrogram.
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